1. Field of the Invention
The invention relates to a system and a method for preventing an illegal copy of contents (including audio and video data, such as moving images) stored in a recording medium like an optical disk. In particular, the invention relates to a recording medium which stores the contents by the use of the system and the method.
2. Description of the Related Art
Various recording mediums and methods have been proposed which can serve to prevent an illegal copy. For example, disclosure is made in Japanese Laid Open Publication No. Hei 11-250572 (namely, 250572/1999) about an optical disk and a recording method.
According to the disclosed method, it is possible to prevent an illegal copy by using a specific media ID of an original optical disk when contents stored in the original optical disk are decoded. That is, even if contents stored in the original optical disk are illegally copied onto another copy optical disk, decoding of the copied contents is properly prevented. This is because, when the contents are illegally copied onto another copy optical disk, a copied media ID on another optical disk is different from or changed from the media ID of the original optical disk.
However, in the conventional method, once the contents (for example, audio and video data) are decoded (decrypted), the can be easily reproduced without any restriction. Therefore, if the decoded contents are obtained by some means, the contents can be illegally copied to another optical disk or another recording medium in the same aspect as the original contents.